Absorbent pads such as sanitary napkins which utilize cellulosic fiber as their principal absorbent are well known. Cellulosic fiber provides a relatively inexpensive source of absorbent material but suffers from distinct disadvantages when utilized alone as an absorbent layer. One of the main disadvantages is that when a layer of cellulosic fiber is wetted, it tends to collapse upon itself. This results in a saturated cellulosic fiber which is dense, compacted, and relatively hard and uncomfortable.
It has been proposed that sanitary napkins be formed of a material containing plastic fibers that allow fusing the absorbent to aid in shaping. Such a pad having a C-fold structure has been proposed in U.S. Pat. No. 4,576,596 issued to Jackson et al. The Jackson patent also teaches that an insert, such as a meltblown strip, may be incorporated into the interior of the sanitary napkin to aid in absorbing and holding body fluids. While such a sanitary napkin is satisfactory, the thermoplastic-containing absorbent has properties that are a compromise between softness, stiffness, fluid transfer and fluid holding properties.
It is desirable that the absorbent material at the top of a feminine pad, adjacent to the wearer's body, be soft and cushiony. The absorbent material should also be high in porosity, that is, it should have a low density to facilitate rapid fluid absorption and be capable of transferring the fluid rapidly away from the body. The absorbent material situated below the top absorbent should have good fluid holding properties and be capable of wicking the fluid throughout the pad. These desirable features are not present in the Jackson patent.
Other U.S. patents, such as U.S. Pat. Nos. 4,505,705; 4,475,913; 3,699,966 and 3,430,629, teach that the absorbent can be folded about itself without referring to the advantages of having a variable density in the z direction. Still other U.S. patents, such as U.S. Pat. Nos. 3,017,304; 3,779,246; 4,226,237; 4,377,615 and 4,223,677, teach the use of various layers of absorbents having different thicknesses and densities. They do not suggest the use of a single absorbent sheet which is folded upon itself.
There are other U.S. patents, such as U.S. Pat. Nos. 4,496,358; 4,449,979 and 3,900,027, which teach the advantages of having a variable density in the z direction. However, no mention is made of folding the absorbent material. Lastly, U.S. Pat. No. 4,315,507 issued to Whitehead teaches forming a fusible baffle on one surface of an absorbent which is then used in a sanitary napkin. However, the baffle is completely covered by an outer wrap and, therefore, does not have an external surface which contacts the undergarment.
Another compromise in single absorbency pads is strength. Generally, an absorbent that has a higher density is stiffer and can prevent bending and twisting of the pad while in use. However, a dense absorbent will not feel as soft to the wearer and, therefore, sacrifices comfort in order to achieve stiffness.
Feminine pads having multiple layers of different densities have also been proposed. However, such pads are expensive and complicated to manufacture as they require formation and uniting of several different absorbent materials with good alignment at high speed and low cost. Accordingly, there is a need for an absorbent article which has a soft feel and which has a variable density in the z direction.